Acrylamide alkyl sulfonic acid and analogues thereof, mainly as a co-monomer and homo-monomer, are widely used in many industries. In some situations where very high degree of polymerization is demanded, the product directly synthesized may still need to be refined to further improve the quality. Many documents, e.g. U.S. Pat. No. 4,337,215, and actual productions relate to the recrystallization purification of acrylamide alkyl sulfonic acid. But the solid added is completely dissolved in all of these refining processes in the prior art, for example, the solid is completely dissolved by increasing the temperature, and then the solid is re-separated out through the methods such as reducing the solvent by decreasing the temperature of the system or by evaporation, rather than intending to use significantly excessive solid. Moreover, all of these methods mainly use organic solvents, such as acetic acid or acetic acid added with a small amount of water, while it is hard to directly use pure water. The advantage of these methods is that the refined product obtained has very good quality, but the disadvantages are high cost, low efficiency, and complex process, etc.